**Core Concept**
The P.D ligament, also known as the posterior cruciate ligament (PCL), is a crucial ligament in the knee joint that provides stability. The horizontal fibers of the PCL play a significant role in maintaining joint stability by preventing excessive movement.

**Why the Correct Answer is Right**
The horizontal fibers of the PCL are responsible for limiting posterior translation of the tibia in relation to the femur. This is achieved through a strong attachment to the posterior aspect of the femoral condyles and the anterior aspect of the tibia. The horizontal fibers work in conjunction with the oblique fibers to maintain the integrity of the knee joint. When the knee is flexed, the horizontal fibers tighten, preventing excessive posterior translation of the tibia.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the horizontal fibers do not primarily provide rotational stability to the knee joint.
**Option B:** This option is incorrect because the horizontal fibers do not primarily provide medial-lateral stability to the knee joint.
**Option C:** This option is incorrect because the horizontal fibers do not primarily provide anterior-posterior stability to the knee joint through a taut or loose structure.

**Clinical Pearl / High-Yield Fact**
The PCL is often injured in conjunction with other knee ligaments, particularly the ACL, during high-energy trauma. A thorough understanding of the PCL's anatomy and function is essential for diagnosing and treating PCL injuries.

**Correct Answer: C. Limiting posterior translation of the tibia in relation to the femur.**